@article{CMUC_1982_23_2_a9,
     author = {Poljak, Svatopluk and Turz{\'\i}k, Daniel and Pudl\'ak, Pavel},
     title = {Extensions of $k$-subsets to $k+1$-subsets - existence versus constructability},
     journal = {Commentationes Mathematicae Universitatis Carolinae},
     pages = {337--349},
     year = {1982},
     volume = {23},
     number = {2},
     mrnumber = {664978},
     zbl = {0495.68059},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/CMUC_1982_23_2_a9/}
}